Boards for building material, such as gypsum boards and calcium silicate boards, are practically and widely used as architectural interior finish materials. In general, these kinds of boards are secured to interior finish base materials to be finished, such as light-weight steel base members or base boards, with use of fixing elements such as screws or nails (referred to as “fixing elements” hereinafter), or with use of adhesives and the fixing elements. The fixing elements are screwed or driven to the board so that exposed parts of the fixing elements are flush with surfaces or slightly sunk below the surfaces, whereby the fixing elements are tightly fixed to the base materials. On the surfaces of the boards, there are irregularities or dents locally formed around the exposed parts of the screwed or driven fixing elements, or cross recesses of the screw heads or the like for engagement with a rotating tool such as a screwdriver. Therefore, putty finishing is carried out for such exposed parts, before painting, wallpapering and so forth.
A construction method in consideration of such putty finishing can be assumed, wherein recesses, grooves or the like for the putty are preformed in screwing or driving positions of the fixing elements. For instance, circular recesses having a diameter slightly larger than that of a profile of the screw head are preformed in the screwing positions, and the putty is filled thereinto after the screws are driven to centers of the recesses, whereby the screw heads in the recesses are embedded in the putty. As a technique similar to this method, it is disclosed in Japanese patent application laid-open publication No. 55-138556 (JP No. 55-138556) that a board for building material has regular grooves corresponding to tile joints and exhibits a tile joint pattern. This board is secured to a base material by hammering nails into the bottom of the groove. The groove is filled with white cement. Heads of the nails are embedded in the solidified white cement, so that the heads are visually concealed from an interior space of a room.
Further, a board for building material preliminarily provided with an interior finish material on its surface, such as a decorated gypsum board or decorated calcium silicate board, is known. As regards this kind of board, it is unnecessary to execute painting, wallpapering or the like for the surface of the board. Therefore, an interior finish surface can be formed in an interior side by merely fixing the board to a ceiling or a wall. When such a decorated board is secured to a base material by screws, a measure is normally taken for irregularities or unevenness of the surface of the board caused by screw heads, exposure of the screw heads, or the like. For example, putty finishing for the screw heads or a specific painting for the screw heads is carried out, or specific screws are used.
A method for allowing the screw heads to be visually inconspicuous without such a treatment for the screw heads is disclosed in Japanese patent application laid-open publication No. 2003-154514 (JP No. 2003-154514), in which an irregular pattern is preformed on a surface of the board. This kind of method might be able to be used for a decorated ceiling board or the like having an irregular pattern, such as a vermicular pattern. However, such a method cannot be employed with respect to a board for building material having a uniform and regular formation of patterns, undulations or apertures.
Furthermore, a perforated board for building material having many through-holes of a small diameter or small dimensions is known. The perforated board is mainly intended for prevention of an echo, or control of a sound absorption performance or an acoustic reverberation time. The perforated board is a plate-like member having an appropriate open area ratio. In general, a layer of air, or a layer packed with a sound absorbing material such as a glass wool is provided behind the plate-like member; or otherwise, a sheet such as a sheet of paper is overlaid on a reverse face of the plate-like member. If required, an interior finish work such as painting or wallpapering is provided in a plant or a construction site with respect to a face of the perforated board on its interior side. It is disclosed in Japanese patent application laid-open publication No. 2000-504797 (JP No. 2000-504797, which corresponds to PCT pamphlet of PCT international application No. WO97/29254, that a part of through-holes of such a perforated board is formed to be fissure-like perforations which do not extend through the board.
In general, a number of through-holes are disposed in the perforated board mainly intended for acoustic control or sound absorption, and the through-holes exhibit a variety of patterns or shadows over the whole surface. However, the fixing element such as a board fixing screw cannot be driven or screwed in the through-hole. Usually, the perforated board is partially provided with non-perforated zones to which the fixing elements can be driven or screwed. For example, this kind of non-perforated zone is formed in a periphery of the board, or it is provided in a form of zone traversing the board.
However, if such a non-perforated zone is formed on the board, the number of through-holes and the locations of through-holes, or their regularity, uniformity and architectural design are restricted by forming the non-perforated zones. In addition, putty finishing and/or painting for concealing an exposed part of the fixing element has to be executed.
For architectural appearance of the exposed part of the fixing element, it might be possible to employ the method of preforming recesses, grooves or the like for putty finishing, as disclosed in JP 55-138556 as set forth above. According to such a method, however, drying shrinkage of the putty, aged deterioration of the putty and so forth may occur, which result in a condition that the recesses or grooves themselves are conspicuous.
On the other hand, the method of preforming irregular patterns on the board as disclosed in JP Nos. 2003-154514 and 2000-504797 as set forth above (i.e., method for allowing existence of the fixing element to be inconspicuous by irregular pattern or the like) cannot be employed for a perforated board having a regular or uniform thorough-holes.
Further, since the perforated board is mainly used for improving an acoustic performance of a room, it is desired in many cases that a certain area is entirely finished by the perforated boards. However, in some cases, it is not desired that the whole finished area has the sound absorption performance, owing to a purpose or structure of the room. For example, in some cases, it is desired that the perforated board is located only in a part effective in improvement of the acoustic performance, and that non-perforated boards are located in a part in which the sound absorption effect is unnecessary or in which an acoustic reflection is required. However, impairment of uniformity or unity of architectural design results from mixed use of the perforated boards and the non-perforated boards. This may lead to an unnatural impression or a sense of incompatibility, which often results in difficulty of interior design. Therefore, in practice, the finished area, such as a ceiling, is entirely finished by the perforated boards, regardless of whether the sound absorption performance is required.
It is an object of the present invention to provide a board for building material and a method of producing the board, which can ensure a region for screwing or driving a fixing element without impairing the regularity, uniformity or architectural design of the perforations, and which can improve workability of construction by omitting putty finishing or the like for an exposed part of the fixing element.
It is another object of the present invention to provide a construction method or execution method of the board for building, which enables arbitrary setting of a sound absorption effect and an acoustic reverberation effect of an interior finish surface, without impairing uniformity or unity of architectural design of the interior finish surface.